ABSTRACT
Virus characterization has undergone continual refinement as a consequence of the development of new technologies. Most of the human viruses we know today were first identified by observing the consequences of viral replication in laboratory animals, embryonated eggs, or cell cultures. Although not all viruses grow in culture and not all viruses produce a cytopathic effect, infection of cultures can result in reproducible and characteristic changes in cell morphology. This is in a crude sense a form of phenotyping. With the development of serology technology in the 1970s, some classes of viruses could then be identified using specific antibodies capable of neutralizing their infectivity. Serotyping, using neutralizing antibodies raised to type-specific antigens, has been an important tool for classifying viruses, including poliovirus (types 1, 2, and 3), hepatitis B virus (adw, adr, ayw, and ayr), dengue virus (types 1, 2, 3, and 4), and many other virus groups. Serotyping, however, is not suitable for all viruses and the dawn of the molecular biology era allowed viruses to be classified genotypically, at first by using nucleic acid hybridization technology and more recently with the aid of amplification technology, such as the polymerase chain reaction (PCR) followed by DNA sequencing and analysis.
